How does a compiler use intermediate code?

A compiler uses intermediate code as a transitional representation of the source code, simplifying the translation into target machine code.

In the process of compiling, the source code written by a programmer is transformed into machine code that can be executed by a computer. This transformation doesn't happen in one step, but rather through a series of stages. One of these stages involves the generation of intermediate code.

The intermediate code is a lower-level representation of the source code, but it is not yet machine code. It sits between the high-level language of the source code and the low-level language of the machine code. This intermediate code is often similar to assembly language, but it is machine-independent, meaning it is not tied to any specific hardware.

The use of intermediate code offers several advantages. Firstly, it simplifies the process of compiling. The compiler can focus on translating the high-level source code into intermediate code, without worrying about the specifics of the target machine. Then, a separate part of the compiler, often called the code generator, can focus on translating the intermediate code into machine code.

Secondly, the use of intermediate code allows for code optimisation. The compiler can analyse the intermediate code and make improvements, such as removing redundant instructions or reordering instructions for better performance. This optimisation can be done without affecting the original source code.

Finally, the use of intermediate code makes the compiler more portable. Since the intermediate code is machine-independent, the same compiler can be used to generate code for different types of machines. All that is needed is a different code generator for each type of machine.

In summary, the compiler uses intermediate code as a stepping stone in the process of transforming source code into machine code. This allows the compiler to break down the complex task of compiling into simpler steps, optimise the code for better performance, and support multiple types of machines.